Method and apparatus for improved input sensing using a display processor reference signal

ABSTRACT

Embodiments of the invention generally provide a method and apparatus that is configured to reduce the effects of interference that is undesirably provided to a transmitter signal that is delivered from a transmitter signal generating device to a sensor processor to determine if an input object is disposed within a touch sensing region of a touch sensing device. In one embodiment, the sensor processor includes a receiver channel that has circuitry that is configured to separately receive a transmitter signal delivered from a display processor and a sensor processor reference signal that is based on a display processor reference signal to reliably sense the presence of an object. Embodiments of the invention described herein thus provide an improved apparatus and method for reliably sensing the presence of an object by a touch sensing device.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention generally relate to a system andmethod for reliably sensing an input object's position over a sensingregion of a proximity sensing device.

2. Description of the Related Art

Input devices including proximity sensor devices, also commonly calledtouchpads or touch sensor devices, are widely used in a variety ofelectronic systems. A proximity sensor device typically includes asensing region, often demarked by a surface, in which the proximitysensor device determines the presence, location and/or motion of one ormore input objects. Proximity sensor devices may be used to provideinterfaces for the electronic system. For example, proximity sensordevices are often used as input devices for larger computing systems,such as opaque touchpads integrated in, or peripheral to, notebook ordesktop computers. Proximity sensor devices are also often used insmaller computing systems, such as touch screens integrated in cellularphones. Many commercially available proximity sensor devices utilize oneor more electrical techniques to determine the presence, location and/ormotion of an input object, such as a capacitive or a resistive sensingtechnique. Typically, the proximity sensor devices utilize an array ofsensor electrodes to detect the presence, location and/or motion of aninput object.

In some configurations, proximity sensor devices are used in combinationwith other supporting components, such as a display or other inputdevices found in the electronic or computing system. In theseconfigurations, the proximity sensor devices are coupled to the displaydriving components, or other similar supporting components, to provide adesired combined function or to provide a complete device package. FIG.1 illustrate a schematic view of a touch sensitive display system 50that includes a display driver module 20 that is configured to drive oneor more common electrodes 10 for updating a display, and for capacitivesensing using one or more sensing electrodes 11 that are coupled to atouch sensing module 21. For simplicity of discussion, the touchsensitive display system 50 shown in FIG. 1 only illustrates one commonelectrode 10 and one sensing electrode 11, however, most capacitivesensing type touch sensitive displays will include a plurality of commonelectrodes 10 and a plurality of sensing electrodes 11 that are disposedin an array type pattern (not shown) to sense the positional informationof an object over a desired region of the device. During operation, asensed capacitance “C_(s)” formed between a common electrode 10 and asensing electrode 11, when the common electrode 10 is driven forcapacitive sensing, will vary as an object moves or is positioned inclose proximity to the electrodes. The varying sensed capacitance“C_(s)” is measured by the touch sensing module 21, thus letting thesystem know that a touch has occurred. Since it is common for thedisplay driver module 20 and the touch sensing module 21 to includeseparate power delivery components, due to the differences in electricalrequirements needed to drive the display components and to sense thepositional information of an object, it is common for the display drivermodule 20 and the touch sensing module 21 to be separated from eachother and to be referenced to different reference voltages or grounds,such as display ground 15 and touch sensing ground 16, respectively.However, it has been found that the benefits of having separate powerdelivery components in each of these modules 20, 21 can lead to issueswith the system's ability to reliably sense the positional informationof an object, due to noise generated by the power delivery components inthe display driver module 20 that affects the resulting signal receivedwith the components in the touch sensing module 21. In theseconventional configurations, the noise added to the transmittersignal(s) delivered through the common electrode(s) 10 from the displaydriver module 20 is not accounted for during the touch sensing processcompleted by the touch sensing module 21, and thus can cause the touchsensing data processed by the touch sensing module 21 to vary and givefalse or misleading touch sensing results.

Therefore, there is a need for a method and an apparatus that providesuseful and reliable touch sensing results despite the use of separatepower delivery components in the touch sensing and display drivingcomponents in a touch sensitive display system.

SUMMARY OF THE INVENTION

Embodiments of the invention generally provide a method and apparatusthat is configured to reduce the effects of noise that is undesirablypresent in a transmitter signal that is delivered from a transmittersignal generating device to a sensor processor to determine if an inputobject is disposed within a touch sensing region of a touch sensingdevice. In one embodiment, the sensor processor includes a receiverchannel that has circuitry that is configured to separately receive atransmitter signal delivered from a display processor and a sensorprocessor reference signal that is based on a display processorreference signal to reliably sense the presence of an object.

Embodiments of the invention generally provide an input device thatincludes a plurality of transmitter electrodes comprising a plurality ofcommon electrodes configured to operate in a first mode for capacitivesensing and configured to operate in a second mode for updating adisplay device, a plurality of receiver electrodes, a display processorcoupled to the plurality of common electrodes and configured to drivethe common electrodes for capacitive sensing and updating a displaydevice, and a sensor processor coupled to the plurality of receiverelectrodes and configured to receive resulting signals with theplurality of receiver electrodes when the common electrodes are drivenfor capacitive sensing. The sensor processor comprises one or morereceiver channels, and wherein each of the one or more receiver channelsis coupled to a receiver electrode of the plurality of receiverelectrodes, and each of the one or more receiver channels have a firstinput port configured to receive a sensor processor reference signalthat is based on a display processor reference signal, and a secondinput port configured to receive at least a portion of the resultingsignals, wherein each of the one or more receiver channels is configuredto provide an output signal based on a comparison of the at least aportion of the resulting signals and the sensor processor referencesignal.

Embodiments of the invention may further provide a sensor processor foran input device that includes sensor circuitry coupled to a plurality ofreceiver electrodes, wherein the sensor circuitry is coupled to adisplay processor that is configured to drive a plurality of commonelectrodes for capacitive sensing and updating a display device, whereinthe sensor circuitry is configured to receive resulting signals with theplurality of receiver electrodes when the display processor drives theplurality of common electrodes for capacitive sensing, wherein thesensor circuitry comprises a receiver channel configured to receive asensor processor reference signal that is based on a display processorreference signal, and wherein the receiver channel is configured toprovide an output signal based on at least a portion of the receivedresulting signals and the sensor processor reference signal.

Embodiments of the invention may further provide a display processor foran input device that includes display driver circuitry coupled to aplurality of common electrodes and configured to drive a plurality ofcommon electrodes for capacitive sensing and updating a display device,wherein a display processor is coupled to a sensor processor configuredto receive resulting signals with a plurality of receiver electrodeswhen the display driver circuitry drives the plurality of commonelectrodes for capacitive sensing, wherein the sensor processorcomprises a receiver channel having a first input port that isconfigured to receive a sensor processor reference signal that is basedon a display processor reference signal, and wherein the receiverchannel is configured to provide an output signal based on at least aportion of the received resulting signals and the sensor processorreference signal.

Embodiments of the invention may further provide a method of sensing aninput object in a sensing region of an input device that includesdriving a display update on at least one of a plurality of commonelectrodes, the common electrodes configured for capacitive sensing andupdating a display device, driving a transmitter signal through on atleast one of a plurality of common electrodes, receiving a resultingsignal from one or more receiver electrodes, wherein the resultingsignal comprises effects corresponding to the transmitter signaldelivered on the at least one of the plurality of common electrodes, andcomparing the resulting signal with a sensor processor reference signalthat is based on a display processor reference signal.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 is a schematic diagram of a conventional touch sensitive displaydevice.

FIG. 2A is a schematic block diagram of an input device in accordancewith embodiments of the invention.

FIG. 2B is a schematic diagram illustrating one example of an inputdevice according to one or more of the embodiments described herein.

FIG. 3A is a schematic diagram illustrating one example of an inputdevice according to one or more of the embodiments described herein.

FIG. 3B is a schematic diagram illustrating one example of an inputdevice according to one or more of the embodiments described herein.

FIG. 4A is a schematic diagram illustrating one example of an inputdevice according to one or more of the embodiments described herein.

FIG. 4B is a schematic diagram illustrating one example of an inputdevice according to one or more of the embodiments described herein.

FIG. 5A is a schematic diagram illustrating one example of an inputdevice according to one or more of the embodiments described herein.

FIG. 5B is a schematic diagram illustrating one example of an inputdevice according to one or more of the embodiments described herein.

FIG. 6A is a schematic diagram illustrating one example of an inputdevice according to one or more of the embodiments described herein.

FIG. 6B is a schematic diagram illustrating one example of an inputdevice according to one or more of the embodiments described herein.

FIG. 7A is a schematic diagram illustrating one example of an inputdevice according to one or more of the embodiments described herein.

FIG. 7B is a schematic diagram illustrating one example of an inputdevice according to one or more of the embodiments described herein.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements disclosed in oneembodiment may be beneficially utilized on other embodiments withoutspecific recitation. The drawings referred to here should not beunderstood as being drawn to scale unless specifically noted. Also, thedrawings are often simplified and details or components omitted forclarity of presentation and explanation. The drawings and discussionserve to explain principles discussed below, where like designationsdenote like elements.

DETAILED DESCRIPTION

The following detailed description is merely exemplary in nature and isnot intended to limit the invention or the application and uses of theinvention. Furthermore, there is no intention to be bound by anyexpressed or implied theory presented in the preceding technical field,background, brief summary or the following detailed description.

Embodiments of the invention generally provide a method and apparatusthat is configured to minimize the effects of noise that is undesirablyprovided to a transmitter signal delivered from a transmitter signalgenerating device, such as a display processor, to a sensor processorthat is configured to receive and process the resulting signal todetermine if an input object is disposed within a touch sensing regionof a touch sensing device. In one embodiment, the sensor processorincludes a receiver channel that has circuitry that is configured toseparately receive a resulting signal comprising effects of atransmitter signal delivered from a display processor and a sensorprocessor reference signal that is based on a display processorreference signal. Embodiments of the invention described herein thusprovide an improved apparatus and method for reliably sensing thepresence of an object by a touch sensing device.

FIG. 2A is a block diagram of an exemplary input device 200, inaccordance with embodiments of the invention. In FIG. 2A, the inputdevice 200 is a proximity sensor device (e.g., “touchpad,” “touchscreen,” “touch sensor device”) configured to sense inputs provided byone or more input objects 240 positioned in a sensing region 220.Example input objects include fingers and styli, as shown in FIG. 2A. Insome embodiments of the invention, the input device 200 may beconfigured to provide input to an electronic system 250, which issometime referred to herein as the “host.” As used in this document, theterm “electronic system” (or “electronic device”) broadly refers to anysystem capable of electronically processing information. Somenon-limiting examples of electronic systems include personal computersof all sizes and shapes, such as desktop computers, laptop computers,netbook computers, tablets, web browsers, e-book readers, and personaldigital assistants (PDAs). Additional examples of electronic systemsinclude composite input devices, such as physical keyboards that includeinput device 200 and separate joysticks or key switches. Furtherexamples of electronic systems 250 include peripherals, such as datainput devices (e.g., remote controls and mice) and data output devices(e.g., display screens and printers). Other examples include remoteterminals, kiosks, video game machines (e.g., video game consoles,portable gaming devices, and the like), communication devices (e.g.,cellular phones, such as smart phones), and media devices (e.g.,recorders, editors, and players such as televisions, set-top boxes,music players, digital photo frames, and digital cameras). Additionally,the electronic system could be a host or a slave to the input device.

The input device 200 can be implemented as a physical part of theelectronic system 250, or can be physically separate from the electronicsystem. As appropriate, the input device 200 may communicate with partsof the electronic system 250 using any one or more of the following:buses, networks, and other wired or wireless interconnections. Examplesinclude I²C, SPI, PS/2, Universal Serial Bus (USB), Bluetooth, RF, andIRDA.

Sensing region 220 encompasses any space above, around, in and/or nearthe input device 200 in which the input device 200 is able to detectuser input by one or more input objects 240. The sizes, shapes, andlocations of particular sensing regions may vary widely from embodimentto embodiment. In some embodiments, the sensing region 220 extends froma surface of the input device 200 in one or more directions into spaceuntil signal-to-noise ratios prevent sufficiently accurate objectdetection. The distance to which this sensing region 220 extends in aparticular direction, in various embodiments, may be on the order ofless than a millimeter, millimeters, centimeters, or more, and may varysignificantly with the type of sensing technology used and the accuracydesired. Thus, some embodiments sense input that comprises no contactwith any surfaces of the input device 200, contact with an input surface(e.g., a touch surface) of the input device 200, contact with an inputsurface of the input device 200 coupled with some amount of appliedforce or pressure, and/or a combination thereof. In various embodiments,input surfaces may be provided by surfaces of casings within which thesensor electrodes reside, by face sheets applied over the sensorelectrodes or any casings, etc. In some embodiments, the sensing region220 has a rectangular shape when projected onto an input surface of theinput device 200.

The input device 200 may utilize any combination of sensor componentsand sensing technologies to detect user input in the sensing region 220.The input device 200 generally comprises one or more sensing elements221 for detecting user input. As several non-limiting examples, the oneor more sensing elements 221 in the input device 200 may use capacitive,elastive, resistive, inductive, magnetic acoustic, ultrasonic, and/oroptical techniques to detect the position or motion of the inputobject(s) 240. Some implementations are configured to provide sensingimages that span one, two, three, or higher dimensional spaces.

In FIG. 2A, a processing system 210 is shown as part of the input device200. The processing system 210 is configured to operate the hardware ofthe input device 200 to detect input in the sensing region 220. Theprocessing system 210 comprises parts of or all of one or moreintegrated circuits (ICs) and/or other circuitry components. In someembodiments, the processing system 210 also compriseselectronically-readable instructions, such as firmware code, softwarecode, and/or the like. In some embodiments, components composing theprocessing system 210 are located together, such as near sensingelement(s) 221 of the input device 200. In other embodiments, componentsof processing system 210 are physically separate with one or morecomponents close to sensing elements 221 of input device 200, and one ormore components elsewhere. For example, the input device 200 may be aperipheral coupled to a desktop computer, and the processing system 210may comprise software configured to run on a central processing unit ofthe desktop computer and one or more ICs (perhaps with associatedfirmware) separate from the central processing unit. As another example,the input device 200 may be physically integrated in a phone, and theprocessing system 210 may comprise circuits and firmware that are partof a main processor of the phone. In some embodiments, the processingsystem 210 is dedicated to implementing the input device 200. In otherembodiments, the processing system 210 also performs other functions,such as operating display screens, driving haptic actuators, etc.

The processing system 210 may be implemented as a set of modules thathandle different functions of the input device 200. Each module maycomprise circuitry that is a part of the processing system 210,firmware, software, or a combination thereof. In various embodiments,different combinations of modules may be used. In one example, modulesinclude hardware operation modules for operating hardware such assensing elements and display screens, data processing modules forprocessing data, such as sensor signals, and positional information, andreporting modules for reporting information. In another example, modulesinclude sensor operation modules configured to operate sensingelement(s) to detect input, identification modules configured toidentify gestures such as mode changing gestures, and mode changingmodules for changing operation modes.

In some embodiments, the processing system 210 responds to user input(or lack of user input) in the sensing region 220 directly by causingone or more actions. In one example, actions include changing operationmodes, as well as GUI actions, such as cursor movement, selection, menunavigation, and other functions. In some embodiments, the processingsystem 210 provides information about the input (or lack of input) tosome part of the electronic system (e.g., to a central processing systemof the electronic system that is separate from the processing system210, if such a separate central processing system exists). In someembodiments, some part of the electronic system process informationreceived from the processing system 210 is used to act on user input,such as to facilitate a full range of actions, including mode changingactions and GUI actions. For example, in some embodiments, theprocessing system 210 operates the sensing element(s) 221 of the inputdevice 200 to produce electrical signals indicative of input (or lack ofinput) in the sensing region 220. The processing system 210 may performany appropriate amount of processing on the electrical signals inproducing the information provided to the electronic system. Forexample, the processing system 210 may digitize analog electricalsignals obtained from the sensing elements 221. As another example, theprocessing system 210 may perform filtering or other signalconditioning. As yet another example, the processing system 210 maysubtract or otherwise account for a baseline set of data (e.g., baselineimage), such that the information reflects a difference between theacquired electrical signals (e.g., sensing image) and the baseline. Asyet further examples, the processing system 210 may determine positionalinformation, recognize inputs as commands, recognize handwriting, andthe like.

“Positional information” as used herein broadly encompasses absoluteposition, relative position, velocity, acceleration, and other types ofspatial information. Exemplary “zero-dimensional” positional informationincludes near/far or contact/no contact information. Exemplary“one-dimensional” positional information includes positions along anaxis. Exemplary “two-dimensional” positional information includesmotions in a plane. Exemplary “three-dimensional” positional informationincludes instantaneous or average velocities in space. Further examplesinclude other representations of spatial information. Historical dataregarding one or more types of positional information may also bedetermined and/or stored, including, for example, historical data thattracks position, motion, or instantaneous velocity over time.

In some embodiments, the input device 200 is implemented with additionalinput components that are operated by the processing system 210 or bysome other processing system. These additional input components mayprovide redundant functionality for input in the sensing region 220, orsome other functionality. FIG. 2A shows buttons 230 near the sensingregion 220 that can be used to facilitate selection of items using theinput device 200. Other types of additional input components includesliders, balls, wheels, switches, and the like. Conversely, in someembodiments, the input device 200 may be implemented with no other inputcomponents.

In some embodiments, the input device 200 comprises a touch screeninterface, and the sensing region 220 overlaps at least part of anactive area of a display screen of a display device 290. For example,the input device 200 may comprise substantially transparent sensorelectrodes overlaying the display screen and provide a touch screeninterface for the associated electronic system. The display screen maybe any type of dynamic display capable of displaying a visual interfaceto a user, and may include any type of light emitting diode (LED),organic LED (OLED), cathode ray tube (CRT), liquid crystal display(LCD), plasma, electroluminescence (EL), or other display technology.The input device 200 and the display device 290 may share physicalelements. Some embodiments of the input device 200 include at least partof the display device 290. For example, some embodiments may utilizesome of the same electrical components for displaying and sensing. Insome examples, the display screen of the display device 290 may beoperated in part or in total by the processing system 210.

It should be understood that while many embodiments of the presenttechnology are described in the context of a fully functioningapparatus, the mechanisms of the present technology are capable of beingdistributed as a program product (e.g., software) in a variety of forms.For example, the mechanisms of the present technology may be implementedand distributed as a software program on information bearing media thatare readable by electronic processors (e.g., non-transitorycomputer-readable and/or recordable/writable information bearing mediareadable by the processing system 210). Additionally, the embodiments ofthe present technology apply equally regardless of the particular typeof medium used to carry out the distribution. Examples ofnon-transitory, electronically readable media include various discs,memory sticks, memory cards, memory modules, and the like.Electronically readable media may be based on flash, optical, magnetic,holographic, or any other storage technology.

In many embodiments, the positional information of the input object 240relative to the sensing region 220 is monitored or sensed by use of oneor more sensing elements 221 (FIG. 2A) that are positioned to detect its“positional information.” In general, the sensing elements 221 maycomprise one or more sensing elements or components that are used todetect the presence of an input object. As discussed above, the one ormore sensing elements 221 of the input device 200 may use capacitive,elastive, resistive, inductive, magnetic acoustic, ultrasonic, and/oroptical techniques to sense the positional information of an inputobject. While the information presented below primarily discuses theoperation of an input device 200, which uses capacitive sensingtechniques to monitor or determine the positional information of aninput object 240 this configuration is not intended to be limiting as tothe scope of the invention described herein, since other sensingtechniques may be used.

In some resistive implementations of the input device 200, a flexibleand conductive first layer is separated by one or more spacer elementsfrom a conductive second layer. During operation, one or more voltagesare applied between adjacent layers. When an input object 240 touchesthe flexible first layer it may deflect sufficiently to createelectrical contact between the layers, resulting in current or voltageoutputs reflective of the point(s) of contact between the layers. Theseresulting current or voltage outputs may be used to determine positionalinformation.

In some inductive implementations of the input device 200, one or moresensing elements pick up loop currents induced by a resonating coil orpair of coils. Some combination of the magnitude, phase, and frequencyof the currents may then be used to determine positional information ofthe input object 240 positioned over the sensing region 220.

In one embodiment of the input device 200, the sensing element 221 is acapacitive sensing element that is used to sense the positionalinformation of the input object(s). In some capacitive implementationsof the input device 200, voltage or current is applied to the sensingelements to create an electric field between an electrode and ground.Nearby input objects 240 cause changes in the electric field, andproduce detectable changes in capacitive coupling that may be detectedas changes in voltage, current, or the like. Some capacitiveimplementations utilize arrays or other regular or irregular patterns ofcapacitive sensing elements to create electric fields. In somecapacitive implementations, portions of separate sensing elements may beohmically shorted together to form larger sensor electrodes. Somecapacitive implementations utilize resistive sheets, which may beuniformly resistive.

Some capacitive implementations utilize “self capacitance” (or “absolutecapacitance”) sensing methods based on changes in the capacitivecoupling between one or more sensing elements, or one or more sensorelectrodes, and an input object. In various embodiments, an at leastpartially grounded input object positioned near the sensor electrodesalters the electric field near the sensor electrodes, thus changing themeasured capacitive coupling of the sensor electrodes to ground. In oneimplementation, an absolute capacitance sensing method operates bymodulating sensor electrodes with respect to a reference voltage (e.g.,system ground), and by detecting the capacitive coupling between thesensor electrodes and the at least partially grounded input object(s).

Some capacitive implementations utilize “mutual capacitance” (or“transcapacitance”) sensing methods based on changes in the capacitivecoupling between two or more sensing elements (e.g., sensor electrodes).In various embodiments, an input object near the sensor electrodesalters the electric field created between the sensor electrodes, thuschanging the measured capacitive coupling. In one implementation, atranscapacitive sensing method operates by detecting the capacitivecoupling between one or more transmitter sensor electrodes (also“transmitter electrodes” or “transmitters”) and one or more receiversensor electrodes (also “receiver electrodes”). Transmitter sensorelectrodes may be modulated relative to a reference voltage (e.g.,system ground) to transmit transmitter signals. Receiver sensorelectrodes may be held substantially constant relative to the referencevoltage to facilitate receipt of resulting signals. A resulting signalmay comprise effect(s) corresponding to one or more transmitter signals,and/or to one or more sources of environmental interference (e.g., otherelectromagnetic signals). Sensor electrodes may be dedicatedtransmitters or receivers, or may be configured to both transmit andreceive.

FIG. 2B is a schematic top view of an input device 295 that has a sensorelectrode pattern that may be used to sense the positional informationof an input object within the sensing region 220. The input device 295may be formed as part of the larger input device 200, which is discussedabove. For clarity of illustration and description, FIG. 2B illustratesa pattern of simple rectangles and thick lines, and does not show all ofthe interconnecting features and/or other related components. While FIG.2B illustrates a pattern of simple rectangles and thick lines, this isnot meant to be limiting and in other embodiments, various sensorelectrode shapes and/or surface areas may be used.

The input device 295 comprising sensor electrodes 260, sensor electrodes270 and a processing system 210. In some embodiments of the invention,as discussed further below, the sensor electrodes 260 may be used toupdate parts of a display and for capacitive sensing, and thus arereferred to herein as “common electrodes,” and the sensor electrodes 270are configured to receive the resulting signal(s) comprising effects ofa transmitter signal(s) delivered through the common electrode(s), andthus are referred to herein as “receiver electrodes.”

The processing system 210 may comprise a sensor processor 360, a displayprocessor 350 and a synchronization mechanism 291 that is coupled to thesensor processor 360 and the display processor 350. The sensor processor360 and the display processor 350 are illustrated in FIGS. 3-7 and arediscussed further below. In cases where the processing system 210comprises more than one processing system ICs, such as shown in FIG. 2B,synchronization between separate processors may be achieved bycommunicating between these systems using a synchronization mechanism291. For example, the synchronization mechanism 291 may synchronizedisplay updating cycle and capacitive sensing cycle by providing asynchronized clock, information about display update state, informationabout the capacitive sensing state, direction to display updatecircuitry to update (or not to update), direction to capacitive sensingcircuitry to sense (or not to sense), reference signals and/or the like.

In some embodiments, sensor electrodes 260 and sensor electrodes 270 maybe similar in size and/or shape. In one example, as shown, these sensorelectrodes are disposed in a sensor electrode pattern that comprises afirst plurality of sensor electrodes 260 (e.g., sensor electrodes 260-1,260-2, 260-3, . . . 260-16 as illustrated in FIG. 2B) and a secondplurality of sensor electrodes 270 (e.g., sensor electrodes 270-1,270-2, 270-3, . . . 270-17 as illustrated in FIG. 2B), which maydisposed above, below, or on the same layer as the first plurality ofsensor electrodes 260. One will note that the sensor electrode patternof FIG. 2B may alternatively utilize various sensing techniques, such asmutual capacitive sensing, absolute capacitive sensing, elastive,resistive, inductive, magnetic acoustic, ultrasonic, or other usefulsensing techniques, without deviating from the scope of the inventiondescribed herein.

Sensor electrodes 260 and sensor electrodes 270 are typically ohmicallyisolated from each other. That is, one or more insulators separatesensor electrodes 260 and sensor electrodes 270 and prevent them fromelectrically shorting to each other in regions where they may overlap.In some embodiments, sensor electrodes 260 and sensor electrodes 270 areseparated by electrically insulative material disposed between them atcross-over areas. In such configurations, the sensor electrodes 260and/or sensor electrodes 270 may be formed with jumpers connectingdifferent portions of the same electrode. In some embodiments, sensorelectrodes 260 and sensor electrodes 270 are separated by one or morelayers of electrically insulative material. In some other embodiments,sensor electrodes 260 and sensor electrodes 270 are separated by one ormore substrates, for example, they may be disposed on opposite sides ofthe same substrate, or on different substrates that are laminatedtogether. In other some embodiments, sensor electrodes 260 and sensorelectrodes 270 may be similar in size and shape. In various embodiments,as will be discussed in more detail later, sensor electrodes 260 andsensor electrodes 270 may be disposed on a single layer of a substrate.In yet other embodiments, other electrodes, including but not limitedto, a shield electrode(s) may be disposed proximate to either sensorelectrodes 260 or 270. The shield electrode may be configured to shieldsensor electrodes 260 and/or sensor electrodes 270 from interferencesuch as nearby sources of driven voltages and/or currents. In someembodiments, the shield electrode(s) may be disposed with sensorelectrodes 260 and 270 on a common side of a substrate. In otherembodiments, the shield electrode(s) may be disposed with sensorelectrodes 260 on a common side of a substrate. In other embodiments,the shield electrode(s) may be disposed with sensor electrodes 270 on acommon side of a substrate. In yet other embodiments, the shieldelectrode may be disposed on a first side of a substrate while sensorelectrodes 260 and/or sensor electrodes 270 are disposed on a secondside, opposite the first.

In one embodiment, the areas of localized capacitive coupling betweensensor electrodes 260 and sensor electrodes 270 may be termed“capacitive pixels.” The capacitive coupling between the sensorelectrodes 260 and sensor electrodes 270 change with the proximity andmotion of input objects in the sensing region associated with the sensorelectrodes 260 and sensor electrodes 270.

In some embodiments, the sensor pattern is “scanned” to determine thesecapacitive couplings. That is, the sensor electrodes 260 are driven totransmit transmitter signals. The input device 295 may be operated suchthat one transmitter electrode transmits at one time, or multipletransmitter electrodes transmit at the same time. Where multipletransmitter electrodes transmit simultaneously, these multipletransmitter electrodes may transmit the same transmitter signal andeffectively produce an effectively larger transmitter electrode, orthese multiple transmitter electrodes may transmit different transmittersignals. For example, multiple transmitter electrodes may transmitdifferent transmitter signals according to one or more coding schemesthat enable their combined effects on the resulting signals of sensorelectrodes 270 to be independently determined. The sensor electrodes 270may be operated singly or multiply to acquire (or receive) resultingsignals (i.e., received capacitive sensing signals). The resultingsignals may be used to determine measurements of the capacitivecouplings at the capacitive pixels, which are used to determine whetheran input object is present and its positional information, as discussedabove. A set of values for the capacitive pixels form a “capacitiveimage” (also “capacitive frame” or “sensing image”) representative ofthe capacitive couplings at the pixels. Multiple capacitive images maybe acquired over multiple time periods, and differences between themused to derive information about input object(s) in the sensing region.For example, successive capacitive images acquired over successiveperiods of time can be used to track the motion(s) of one or more inputobjects entering, exiting, and within the sensing region. In variousembodiments, the sensing image, or capacitive image, comprises datareceived during a process of measuring the resulting signals receivedwith at least a portion of the sensing elements 221 distributed acrossthe sensing region 220. The resulting signals may be received at oneinstant in time, or by scanning the rows and/or columns of sensingelements distributed across the sensing region 220 in a raster scanningpattern (e.g., serially poling each sensing element separately in adesired scanning pattern), row-by-row scanning pattern, column-by-columnscanning pattern or other useful scanning technique. In manyembodiments, the rate that the “sensing image” is acquired by the inputdevice 200, or sensing frame rate, is between about 60 and about 180Hertz (Hz), but can be higher or lower depending on the desiredapplication.

In some touch screen embodiments, the sensor electrodes 260 and/or thesensor electrodes 270 are disposed on a substrate of the associateddisplay device. For example, the sensor electrodes 260 and/or the sensorelectrodes 270 may be disposed on a polarizer, a color filter substrate,or a glass sheet of an LCD. As a specific example, the sensor electrodes260 may be disposed on a TFT (Thin Film Transistor) substrate of an LCD,and may or may not also be used in display operations of the displaydevice. As another example, the receiver electrodes 270 may be disposedon a color filter substrate, on an LCD glass sheet, on a protectionmaterial disposed over the LCD glass sheet, on a lens glass (or window),and the like.

In some touchpad embodiments, the sensor electrodes 260 and/or thesensor electrodes 270 are disposed on a substrate of the touchpad. Insuch an embodiment, the sensor electrodes and/or the substrate may besubstantially opaque. In one embodiment, an opaque material may bedisposed between the sensor electrodes, the substrate and/or the surfaceof the sensing region 220. In some embodiments, the substrate and/or thesensor electrodes may comprise a substantially transparent material. Invarious embodiments, one or more substrates of the touchpad may betextured to facilitate improved user input.

In those embodiments, where sensor electrodes 260 and/or sensorelectrodes 270 are disposed on a substrate within the display device(e.g., color filter glass, TFT glass, etc.), the sensor electrodes maybe comprised of a substantially transparent material (e.g., ITO, ATO) orthey may be comprised of an opaque material and aligned with the pixelsof the display device (e.g., disposed such that they overlap with the“black mask” between pixel dots or a subpixel of the pixel).

In some touch screen embodiments, as shown in FIG. 2B, transmitterelectrodes comprise one or more common electrodes (e.g., segments of asegmented “V-corn electrode”), hereafter referred to as “commonelectrodes 260,” used in updating the display of the display screen.While the sensor electrodes, or common electrodes 260, can be used toperform other capacitive sensing techniques, as discussed above, forclarity and simplicity of the discussion a common electrode capacitivesensing configuration is primarily used in the discussion below. Thesecommon electrodes 260 (e.g., reference numerals 260 ₁, 260 ₂, 260 ₃, . .. 260 ₁₆ shown in FIG. 2B) may be disposed on an appropriate displayscreen substrate. For example, the common electrodes may be disposed onthe TFT glass in some display screens (e.g., In Plane Switching (IPS) orPlane to Line Switching (PLS)), on the bottom of the color filter glassof some display screens (e.g., Patterned Vertical Alignment (PVA) orMulti-domain Vertical Alignment (MVA)), etc. In such embodiments, thecommon electrode can also be referred to as a “combination electrode”,since it performs multiple functions. In various embodiments, eachtransmitter electrode comprises one or more common electrodes 260.

In various embodiments, the common electrodes 260 transmit signals fordisplay updating and capacitive sensing in the same time period, or indifferent time periods. For example, the common electrodes may transmitsignals for display updating during a display-update time of a rowupdate cycle, and transmit signals for capacitive sensing during anon-display time of the row update cycle (e.g. sometimes called“horizontal blanking time”). In another example, the common electrodesmay transmit signals for display updating during a display-update timeof a row update cycle, and transmit signals for capacitive sensingduring a multiple combined non-display times of the row update cycles(e.g., sometimes called “long horizontal blanking time” or “in-frameblanking time”). As another example, the common electrodes may transmitsignals for display updating during row update cycles with actualdisplay row updates, and transmit signals for capacitive sensing duringextra “row update cycles” without actual display row updates (e.g., thenon-display times between updating sections of frames or entire frames,sometimes called “vertical blanking time”). Further, in variousembodiments, the common electrodes may transmit signals for capacitivesensing during any combination of the above non-display times. As afurther example, the common electrodes may transmit signalssimultaneously for display updating and capacitive sensing, but separatethem spatially. As yet another example, the common electrodes may usethe same transmission for both display updating and capacitive sensing.

In FIG. 2B, sensor processor 360 is coupled to the receiver electrodes270 so that it is able to receive the resulting signals from thereceiver electrodes. Display processor 350 is coupled with commonelectrodes 260, and comprises display circuitry (not shown) configuredfor displaying images on the display screen. The display circuitry isconfigured to apply one or more pixel voltage(s) to the display pixelelectrodes through pixel source drivers (not shown). The displaycircuitry is also configured to apply one or more common drivevoltage(s) to the sensor electrodes 260, and operate them as commonelectrodes of the display screen. In some embodiments (e.g., lineinversion embodiments), the display circuitry is also configured toinvert the common drive voltage in synchronization with a drive cycle ofthe image display. The display processor 350 is also configured tooperate common electrodes 260 as transmitter electrodes for capacitivesensing. In one embodiment the common electrodes 260 are configured tobe scanned while the receiver electrodes 270 are receiving a signal fromthe common electrodes 260. In some configurations, the receiverelectrodes 270 may be similar to the sensor electrodes 270 that arediscussed above.

Input Device Configurations

FIGS. 3A and 3B are schematic views of a portion of the processingsystem 210 of the input device 200 according to one or more of theembodiments described herein. As discussed above, the display processor350 and sensor processor 360 work together to provide touch sensing datato an analysis module 390. The analysis module 390 may form part of theprocessing system 210, and/or part of the electronic system 250. In oneembodiment, analysis module 390 may form part of the sensor processor360. In various embodiments, the analysis module 390 will comprisesdigital signal processing elements and/or other useful digital andanalog circuit elements that are connected to process the receiverchannel output signal(s) received from at least one receiver channel,and also provide processed signals to other portions of the electronicsystem 250. The electronic system 250 can then use the processed signalsto control some aspect of the input device 200, such as send a messageto the display, perform some calculation or software related task basedon instructions created by one or more software programs that are beingrun by the electronic system and/or perform some other function.

In various embodiments, the display processor 350 comprises a drivevoltage supply 320 and display circuitry that is able to drive displayupdate signals onto a plurality of common electrodes for displayupdating and to transmit transmitter signals with a plurality of commonelectrodes for capacitive sensing. In one embodiment, display processor350 transmits a transmitter signal with transmitter electrode 260-1which is capacitively coupled with receiver electrode 270-1, where thecapacitive coupling is labeled as sensor capacitor C_(s) (i.e.,reference label 221) in FIGS. 3A and 3B. A measurement of a change intranscapacitive (or mutual-capacitive) may be based on a change in thecapacitive coupling between transmitter electrode 260-1 and receiverelectrode 270-1. Although not shown, in various embodiments, driver 321and receiver channel 370 may both be coupled to each of the sensorelectrodes of the input device 200. In such embodiments, when eachsensor electrode is driven with a transmitter signal, a change incapacitive coupling between a sensor electrode and an input object(s) inthe sensing region may be measured, providing a measurement of aself-capacitance (or absolute capacitance). In some configurations, thecommon electrodes forming transmitter electrodes 260 may be disposed onthe TFT glass in some display screens (e.g., In Plane Switching (IPS) orPlane to Line Switching (PLS)), or on the bottom of the color filterglass of some display screens (e.g., Patterned Vertical Alignment (PVA)or Multi-domain Vertical Alignment (MVA), etc.). In some configurations,the display circuitry may comprise a driver 321 that is configured todeliver transmitter signals provided from the drive voltage supply 320to each of the common electrodes. The transmitter signals may beselectively transmitted to one or more of the common electrodes at atime by use of electrical components, such as switches, shift registersand/or other useful components, to perform the touch sensing operation.

During the capacitive sensing operation, the drive voltage supply 320 isconfigured to deliver a transmitter signal, which may comprise a square,sine, rectangular, trapezoidal, Gaussian or other shaped waveform, thatis delivered through one or more of the transmitter electrodes 260 and aresulting signal is then received by one or more receiver electrodes270. In some embodiments, the drive voltage supply 320 is configured todeliver a transmitter signal comprising a voltage pulse that transitionsfrom a first reference voltage level to a second reference voltagelevel. In some configurations, the drive voltage supply 320 isconfigured to deliver a transmitter signal that comprises a transmittersignal, which may comprise a voltage pulse, that transitions from adisplay processor reference voltage level, or display driver low voltagelevel (e.g., display driver reference level (DCV_(com))), to a sourcevoltage level (V_(TX)). In one example, the transmitter signaltransitions from DCV_(com) to V_(TX) and may have a magnitude of between1 and 15 volts and a duration that is between 0.1 and 50 microseconds(μs). However, in other embodiments, the transmitter signal transitionsfrom DCV_(com) to V_(TX) and may have a magnitude of less than 1 volt orgreater than 15 volts, with a duration that may be below 0.1microseconds and greater than 50 microseconds.

In many embodiments, the sensor processor 360 comprises sensor circuitrythat is able to receive and/or process resulting signals with receiverelectrode 270-1. Further, sensor processor 360 may comprise sensorcircuitry that is able to process and/or transmit analog and/or digitalsignals to various electrical components that are used to process,distribute and/or control portions of the input device 200, as discussedabove. The sensor processor 360 may comprise sensor circuitry thatcontains a plurality of logic elements, flip-flops, multiplexers,operational amplifiers, ND converts, D/A converters, current scalers,mixers and/or other useful circuit elements that are connected in adesired way to perform part of the process of sensing an input object240 (as seen in FIG. 2A). The sensor processor 360 is may be configuredto receive input from the various components found in the input device200, process the received inputs and deliver control or command signalswhen necessary to perform a desired portion of the process of sensingthe positional information of an input object 240.

In one embodiment, the sensor processor 360 comprises one or morereceiver channels 370 that each has a first input port 371 that isconfigured to receive the resulting signal received with at least onereceiver electrode 270, a second input port 372 that is configured toreceive a sensor processor reference signal and an output port 373.During operation the sensor processor reference signal, received by thesecond input port 372, is compared with the resulting signal, receivedby the first input port 371, using electrical circuit elements in thereceiver channel 370 to produce a receiver channel output signal. Thecircuit elements in the receiver channel 370 then deliver the receiverchannel output signal to the analysis module 390 and electronic system250.

In some embodiments, the sensor processor 360 has a system ground 346that is coupled to the ground of the analysis module 390 and/or theground of an electronic system 250, so that the receiver channel outputsignal can be received and reliably processed by the analysis module 390and/or an electronic system 250. As shown in FIGS. 3A and 3B, the sensorprocessor system ground 346 may be coupled to the ground of the analysismodule 390 and/or the ground of the electronic system 250, and also thesecond input port 372 of the receiver channels 370 through a resistor342. However, in many embodiments, the output of the drive voltagesupply 320 is referenced to a low voltage level relative to the systemground 346 to assure that the display updating functions provided by thedisplay processor 350 work properly. In some configurations, the drivevoltage supply 320 is referenced to a display processor ground 347 atabout −0.1 to about −2 volts difference relative to the system ground346 of the sensor processor or the host device, or in other words thevoltage level of a point 322 on a line coupled to the display processorground 347 is between about 0.1 to about 2 volts lower relative to apoint 341 measured at the system ground 346 of the sensor processor 360or the host device. In one embodiment, the difference between the point341 of the system ground 346 and the point 322 of the display processorground 347 during operation is about negative one volt (i.e., −1 volt).In another embodiment, the display processor ground 347 may not bedirectly coupled with system ground 346. However, in this configuration,the display processor ground 347 may be substantially at the same levelas system ground 346. In either embodiment, there may be differencesbetween these ground references which may cause related electricalinterference to appear in the resulting signals received by a receiverchannel with a corresponding receiver electrode. This will be discussedin further details below.

In various embodiments of the processing system 210 illustrated in 3Aand 3B, an optional reference channel 380 is added to the sensorprocessor 360 to provide one or more reference channel output signalsthat are used by the analog-to-digital conversion elements in thereceiver channel 370 and/or the analysis module 390 to set a desiredrange to which the received resulting signal are compared to furtherprovide reliable input sensing information to the analysis module 390and electronic system 250. In one example, an output of the drivevoltage supply 320 is delivered to an input of the reference channel380, which is then processed to form one or more reference channeloutput signals. In one embodiment, the output of the drive voltagesupply 320 that is delivered to an input of the reference channel 380 isa transmitter signal. In another embodiment, a first output and a secondoutput of the drive voltage supply are delivered to an input of thereference channel 380 through line 381, which are then processed to formone or more reference channel output signals. In one embodiment, thereference channel 380 may include one or more reference channels (e.g.,reference channels 380 ₁, 380 ₂ illustrated in FIGS. 4A, 4B, 5A, 5B, 6A,and 6B) that each have a first reference input port 383 that isconfigured to receive a reference channel input signal based on a signalreceived from the drive voltage supply 320, a second reference inputport 384 that is configured to receive the sensor processor referencesignal. In some embodiments the sensor processor reference signal may bebased on display processor reference signal delivered through theconnection 343. In various embodiments, during operation the referencechannel input signal received from the display processor 350 is comparedwith the sensor processor reference signal using electrical circuitelements in the reference channel 380, and then the circuit elements inthe reference channel 380 deliver a processed reference channel outputsignal through the output port 385 to a signal line 382 that is coupledto the receiver channel 370 (FIGS. 3-6) and/or the analysis module 390(FIG. 7A). The processed reference channel output signal delivered fromthe reference channel(s) 380 is then compared with the processedresulting signal from the receiver channel(s) 370 to provide reliableprocessed capacitive sensing data to the analysis module 390.

In various embodiments to reconcile the differences between the groundreferences and account for interference created by having power deliverycomponents that are each separately connected to different referencevoltages (i.e., grounds), embodiments of the invention described herein,provide a processing system 210 that includes a sensor processorreference signal, which is based on a display processor referencesignal, which is used by the receiver channels 370 to provide a reliablereceiver channel output signal to the analysis module 390. Referring toFIG. 3A, in one embodiment, the processing system 210 includes aconnection 343 that is used to define a reference level of the sensorprocessor 360 based on a reference level of drive voltage supply 320. Inone embodiment, connection 343-1 capacitively couples a reference levelof the drive voltage supply 320 with the sensor processor 360. Further,in another embodiment, connection 343-1 couples a reference level ofdrive voltage supply 320 with the second input 372 of the receiverchannel(s) 370. The connection 343-1 can then be used to provide thesensor processor reference signal that is compared with the resultingsignals, which are received by the receiver electrodes 270, using areceiver channel 370 to detect the positional information of an inputobject 240 positioned near one or more of the electrodes.

Referring to FIG. 3B, in one embodiment, the processing system 210includes a connection 343-2 that is used to couple the display referencesignal to the reference channel 380 through an input connection 395. Inone embodiment, the connection 343-2 and input connection 395 (e.g.,reference numeral 474 in FIGS. 4B, 5B, 6B and 7B) are coupled to thefirst input port (i.e., input port 383) of reference channel 380,thereby providing the display reference signal to the first input port.In various embodiments, connection 343-2 may comprise a capacitor (e.g.,C_(G1) and/or C_(G2) in FIGS. 4B, 5B, 6B and 7B) that may be internal orexternal to sensor processor 360. Connection 343-2 AC couplesinterference due to the display reference signal with the input to thereference channel such the reference channel output signal may be usedto substantially reduce interference due to the display reference signalin a resulting signal by the receiver channel 370, providing a receiverchannel output signal. The receiver channel output signal may then beused to detect the positional information of an input object 240positioned near one or more of the electrodes.

Sensing configurations that do not utilize a sensor processor referencesignal that is based on or in some way substantially similar to adisplay processor reference signal, or a reference channel input signalthat is based on the display processor reference signal will be affectedby the interference that is created by the difference between the sensorprocessor reference signal and the display processor reference signal,since the resulting signal(s) may comprise interference that is notaccounted for when the interference affected resulting signal iscompared with an unreferenced input signal provided to the second input372 of a receiver channel 370. The addition of the interference in aconventionally configured device will cause the output of the receiverchannel components to vary, which thus can affect the reliability of thedata delivered to the analysis module 390 and the ability of the inputdevice to reliably sense an input object 240. In one embodiment, sensorprocessor 360 comprises at least a portion of analysis module 390.

In one embodiment, the sensor processor reference signal is formed bycoupling the second input 372 of the receiver channel 370 to the displayprocessor ground 347 of the display processor 350. In such embodiments,display processor ground 347 may be referred to as a display processorreference signal. In some configurations, as illustrated in FIGS. 4A,5A, 6A and 7A, a system capacitance C_(GS), AC couples the componentsconnected to the second input 372 of the receiver channel 370 via an ACcoupling capacitor to the display processor ground 347 of the displayprocessor 350, which is illustrated in FIG. 3A as connection 343-1.Alternatively, the AC coupling capacitor could be internal to the sensorprocessor 360. In yet another embodiment, the sensor processor referencesignal is formed by connecting the second input 372 to one or morecircuit elements (e.g., resistors (not shown), power supply (not shown),level-shifters) that are connected to the display processor ground 347.In this configuration, the one or more circuit elements can beconfigured to adjust the voltage difference between the displayprocessor ground 347 and the system ground 346 to provide a sensorprocessor reference signal level.

FIGS. 4A and 4B are each a schematic view of a portion of the processingsystem 210 according to one or more of the embodiments described herein.As illustrated in FIGS. 4A and 4B, the processing system 210 maycomprise a display processor 350 and a sensor processor 360 that worktogether to provide receiver channel output signals to the analysismodule 390 and/or the electronic system 250. In one embodiment, sensorprocessor 360 comprises at least a portion of analysis module 390. Asdiscussed above, the positional information of an input object 240 isderived based on the capacitance C_(s) (e.g., capacitance C_(S1),C_(S2), . . . C_(SN)) measured between each of the transmitterelectrodes 260 (e.g., transmitter electrodes 260 ₁, 260 ₂, . . . 260_(N)) and the receiver electrodes 270 (e.g., receiver electrodes 270 ₁,270 ₂, . . . 270 _(N)).

In one embodiment, as shown in FIGS. 4-7, the display processor 350comprises the drive voltage supply 320 and a driver 321, which areadapted to deliver capacitive sensing signals (transmitter signals) anddisplay updating signals to the common electrodes of the transmitterelectrodes 260 (e.g., transmitter electrodes 260 ₁, 260 ₂, . . . 260_(N)). In one configuration, as illustrated in FIGS. 4-7, the drivevoltage supply 320 may comprise a power supply and signal generator 420Bthat is configured to deliver a square, rectangular, trapezoidal,sinusoidal, Gaussian or other shaped waveform to the transmitterelectrodes 260. In one configuration, the signal generator 420Bcomprises an electrical device, or simple switch, that is able todeliver a transmitter signal that transitions between the output levelof the power supply and a low display voltage level, such as the voltagelevel of point 322 (FIG. 3A) coupled to the display processor ground347. In various embodiments, signal generator 420B may comprise anoscillator. In various other embodiments, signal generator 420B isclocked from an external source. In yet further embodiments signalgenerator 420B may comprise one or more pull-up and/or pull-downtransistors, such as field-effect transistors or the like. In someconfigurations, one or more resistors (not shown), active circuitelements (not shown) or power supplies (not shown) may be disposedbetween point 322 and display processor ground 347 to adjust the lowvoltage level over which the provided transmitter signal varies duringthe capacitive sensing operation. In some embodiments, the low displayvoltage level is between the output level of the power supply anddisplay processor ground 347. In some configurations, the signalgenerator 420B is integrated into the driver 321, which includes one ormore shift registers and/or switches that are adapted to sequentiallydeliver display updating signals and transmitter signals to one or moreof the transmitter electrodes (or common electrodes) at a time. In someconfigurations, the display processor 350 may also comprise a pluralityof connectors (not shown), that are configured to transmit signals toand from the display processor 350.

In one embodiment, as shown in FIGS. 4-7, the sensor processor 360comprises a plurality of receiver channels 370 (e.g., receiver channels370 ₁, 370 ₂, . . . 370 _(N)) that each have a first input port 441(e.g., ports 441 ₁, 441 ₂, . . . 441 _(N)) that is configured to receivethe resulting signal received with at least one receiver electrode 270(e.g., receiver electrode 270 ₁, 270 ₂, . . . 270 _(N)), a second inputport (e.g., ports 442 ₁, 442 ₂, . . . 442 _(N)) that is configured toreceive a sensor processor reference signal delivered through the line425, and an output port coupled to the analysis module 390 andelectronic system 250. Each of the plurality of receiver channels 370may include a charge accumulator 410 (e.g., charge accumulators 410 ₁,410 ₂, . . . 410 _(N)), supporting components 412 (e.g., components 412₁, 412 ₂, . . . 412 _(N)) such as demodulator circuitry, a low passfilter, sample and hold circuitry, other useful electronic componentsfilters and analog/digital converters (ADCs) or the like. Theanalog/digital converter (ADC) may comprise, for example, a standard 8,12 or 16 bit ADC that is adapted to receive an analog signal and delivera digital signal (receiver channel output signal) to the analysis module390. In one configuration, the charge accumulator 410 includes anintegrator type operational amplifier (e.g., Op Amps A₁-A_(N)) that hasan integrating capacitance C_(fb) that is coupled between the invertinginput and the output of the device. In other configurations, the chargeaccumulator 410 includes a current conveyer. In some configurations ofthe charge accumulator 410, a switch (not shown) or resistor (not shown)may be put in parallel with the integrating capacitance C_(fb) todischarge it at a desired time during the capacitive sensing process.The analog/digital converter (ADC) may comprise, for example, a standard8, 12 or 16 bit ADC that is adapted to receive an analog signal anddeliver a digital signal (receiver channel output signal) to theanalysis module 390. In some configurations, the sensor processor 360may also comprise a plurality of connectors, not shown that areconfigured to transmit signals to and from the sensor processor device360.

In one embodiment, as shown in FIGS. 4-7, the sensor processor 360 mayfurther comprise a plurality of reference channels 380 (e.g., referencechannels 380 ₁, 380 ₂) that each have a first input port 434, 435 thatis configured to receive a reference channel input signal that may becoupled to the drive voltage supply 320, a second input port 436, 437that is configured to receive the sensor processor reference signal, andan output port 415, 417, respectively, that are coupled to ADCs found inthe supporting components 412, analysis module 390 and/or electronicsystem 250. Each of the plurality of reference channels 380 may have acapacitor (e.g., input capacitor C_(R1) or C_(R2)) that is coupled tothe first input port (e.g., ports 434, 435), and is sized to adjust thedesired reference channel output signal that each reference channel 380will deliver to one or more of the ADCs found in the supportingcomponents 412 ₁-412 _(N) and/or the analysis module 390. For example,in one embodiment, the reference channel output signal may be one of ahigh reference level signal and a low reference level signal. The spanbetween different reference level outputs can thus be used as areference that the resulting signals processed by the receiver channels370 can be compared against during the touch sensing operation. Whilemultiple reference channels are shown, various embodiments may comprisea single reference channel.

Each of the plurality of reference channels 380 (e.g., referencechannels 380 ₁ and 380 ₂) may include a charge accumulator 432, 433,supporting components 414 ₁, 414 ₂, which in some configurations thesupporting components may comprise demodulator circuitry, a low passfilter, sample and hold circuitry, other useful electronic componentsfilters and analog/digital converters (ADCs) or the like. In oneconfiguration, the charge accumulator 432, 433 includes an integratortype operational amplifier (e.g., Op Amps A_(RH)-A_(RL)) that has anintegrating capacitance C_(fb) that is coupled between the invertinginput and the output of the device. In other configurations, the chargeaccumulator 410 includes a current conveyer. In some configurations ofthe charge accumulator 432, 433, a switch (not shown) or resistor (notshown) may be put in parallel with the integrating capacitance C_(fb) todischarge it at a desired time during the process. In some embodimentsthe reference channels may be configured to deliver a reference channeloutput signal to one or more of the supporting components 414 ₁-414 _(N)found in the receiver channels 380 ₁-380 _(N) and/or the analysis module390.

First Input Device Example

In some embodiments of the processing system 210, as shown in FIG. 4A, aresistive divider 426 is used to adjust the reference level of thesensor processor reference signal delivered to the second input ports372 (e.g., ports 442 ₁, 442 ₂, . . . 442 _(N)) of the receiver channels370 and/or second input ports 436, 437 of the reference channel(s) 380.In various embodiments, the resistive divider 426 comprises a firstresistor 423, which is coupled to a power supply 424 at one end and aresistor 342, as discussed above, that is coupled to system ground 346.In this configuration the power supply 424 can adjust the referencelevel of the sensor processor reference signal delivered to the receiverchannels 370 and reference channels 380. It should be understood thatthe reference can be provided in other ways such as, for example, a morecomplex resistor string, a buffered voltage or a digital-to-analogconverter. In one configuration, a power source may be disposed betweenthe system ground 346 and the sensor processor 360 to adjust thereference level of the sensor processor reference signal delivered tothe second input ports 372 and/or second input ports 436,437. Inembodiments where multiple power sources are discussed, a single powersource may be configured to perform the functions assigned to each ofthe multiple power sources. In some configurations, as shown in FIGS.4A-4B and 7A-7B, the system ground 346 may comprise a first systemground 346-1 and a second system ground 346-2. In one configuration, thefirst system ground 346-1 and the second system ground 346-2 areconnected to the same ground, and are thus at the same potentialrelative to each other. In another configuration, the first systemground 346-1 and the second system ground 346-2 are connected todifferent grounds that are maintained at different potentials relativeto each other.

Referring to FIGS. 4A and 4B, in one embodiment of the processing system210, the first input ports 441 ₁-441 _(N), are ohmically coupled to thereceiver electrodes 270 ₁-270 _(N). In addition to the transmittersignal, interference on the display processor reference signal maycouple from the transmitter electrodes (260 ₁-260 _(N)) into thereceiver electrodes 270 ₁-270 _(N). As such, resulting signals receivedat an input port(s) 441 with a sensor electrode may comprise effectscorresponding to the electrical interference at least partially based onthe difference in reference signals between display processor 350 andthe sensor processor 360. Therefore, in one embodiment, as shown in FIG.4A, the second input ports 442 ₁-442 _(N) of the receiver channels 370are referenced to the display processor 350's display reference signal.In another embodiment, as shown in FIG. 4B, the second input ports 442₁-442 _(N) of the receiver channels 370 are referenced to the sensorprocessor signal and the first input ports 434 and 435 of referencechannels 380 ₁ and 380 ₂ are coupled to the display processor referencesignal through capacitors C_(G1) and C_(G2). In such an embodiment, anyinterference that is present at the display processor reference voltageis coupled to the input port of each reference channel, such that theyreference channel output signal comprises effects corresponding to thatinterference. The reference channel output signal may then be used bythe receiver channel 370 to substantially eliminate any similarinterference in the received resulting signals. This allows the chargeaccumulators to 410 ₁-410 _(N) to substantially cancel out theinterference coupled from the display device into the receiverelectrodes.

Referring to FIGS. 4A and 4B, in one embodiment, the processing system210 comprises a reference channel 380 configuration in which signalgenerators 430-1 and 430-2 drive the first input ports 434,435(respectively) of the reference channels 380, wherein the signalgenerators 430-1 and 430-2 are supplied by the drive voltage supply 320through the line 472. In this configuration, the signal generator 430 isconfigured to provide a reference channel input signal waveform to eachof the input capacitors C_(R1),C_(R2) connected to the first input ports434,435 of the charge accumulators 432,433, respectively. In variousembodiments, the reference channel input signal is a modulated signalthat transitions between a first reference voltage level and a secondreference voltage level. In one example, the reference channel inputsignal is a square wave that transitions between the voltage leveldelivered from the drive voltage supply 320 (V_(TX)) and the signalprocessor reference signal based on the display processor referencesignal. Therefore changes in the diver voltage supply 320 will betracked by the reference channels in the sensor processor. In oneembodiment, the display processor reference signal is based on thedisplay processor ground. In another embodiment, signal generators 430are referenced to the system ground 346. The received reference channelinput signal is then processed by the circuitry in each of the referencechannels 380 ₁, 380 ₂ to provide reference channel output signals thattrack the interference affected signal provided by the drive voltagepower supply 220A, so that the interference affected reference channeloutput signal can then be compared with the at least partially processedreceiver channel output signals created by the receiver channels 370₁-370 _(N), which have also received the interference affected signalfrom the drive voltage power supply 220A. In the embodiment illustratedin FIG. 4B, each reference channel input signal is based on a modulatedsignal from signal generators 430-1 and 430-2 (respectively) and thedisplay processor reference signal biased by C_(G1) and C_(G2). In suchan embodiment, any interference present within the display processorreference signal will be present at the reference channel input signal,and the reference channel output signals will comprise effectscorresponding to that interference. In various embodiments, C_(G1) andC_(G2) may be substantially similar to a capacitive coupling that existsbetween the sensor electrodes (transmitter electrodes 260 and receiverelectrodes 270) and the display device. In one embodiment, whilemultiple signal generators are illustrated in FIGS. 4A and 4B, a singlesignal generator may be implemented, the output of which is coupled toeach of the reference channels. Further, while capacitors C_(G1) andC_(G2) are illustrated as being external to sensor processor 360,however, in other embodiments, one or both capacitors C_(G1) and C_(G2)may be internal to sensor processor 360. Further, while two capacitors,capacitors C_(G1) and C_(G2), are illustrated, in other embodiments,only a single capacitor may be implemented. In one embodiment, since thereceiver channel output signal(s) are compared with a reference channeloutput signal that is similarly affected by the injection ofinterference, a reliable analog-to-digital converted signal withinterference substantially cancelled out can be delivered to theanalysis module 390 to provide reliable, or interference minimized,positional information to the host components. For example, thereference channel output signal(s) may be used to set the voltage rangeof one or more elements of the receiver channel (e.g., ananalog-to-digital converter, or the like), reducing the interference dueto the differences between the display processor and sensor processorreference signals. In one embodiment, the reference channel 380 ₁ isconfigured to deliver a reference channel high output voltage level(RHOL) to the analysis module 390 and the reference channel 380 ₂ isconfigured to deliver a reference channel low output voltage level(RLOL) to the analysis module 390, where the difference between thereference channel high output voltage level and the reference channellow output voltage level spans substantially the same range as thetransmitter signal used for capacitive sensing. Therefore, with the useof the combination of the sensor processor reference signals provided tothe receiver channels 370 and the reference channel output signals theinterference generated by the drive voltage supply 320 can be accountedfor and its affect can be reduced. It should be noted that having only asingle reference channel is also possible, or deriving both RHOL andRLOL from a single reference channel is possible.

Second Input Device Example

FIGS. 5A and 5B are each a schematic view of at least a portion of theprocessing system 210 of the input device 200 according to anotherembodiment of the invention described herein. As illustrated in FIGS. 5Aand 5B, the processing system 210 may comprise a display processor 350and a sensor processor 360 that work together to provide input sensingdata to an analysis module 390 and/or electronic system 250. One willnote that the components that are similarly numbered and configured, asshown in FIGS. 3-5, and thus are not re-discussed herein.

In one embodiment, as discussed above, a sensor processor referencesignal can be formed by capacitively coupling the second input ports 442₁-442 _(N) of the receiver channels 370 to the display processor ground347 of the display processor 350. In some configurations, a systemcapacitance C_(GS) couples the second input ports 442 ₁-442 _(N) and thedisplay processor ground 347 of the display processor 350.Alternatively, the AC coupling capacitor, or the system capacitanceC_(GS), could be internal to 360. In other configurations, asillustrated in 5B, the display processor reference signal may be ACcoupled (C_(G1) and C_(G2)) to the input of each of the referencechannels, such that each reference channel input signal is based, atleast in part, on the interference within the display processorreference signal. Further, in such configurations, the reference channeloutput signals comprise effects corresponding to the interference withinthe display processor reference signal. The AC coupling may be internalto, or external to the sensor processor or the display processor. Onewill note, as is described above, the resulting signals received witheach of the receiver electrodes 270 ₁-270 _(N) and the first input ports441 ₁-441 _(N) may include interference created by the differencebetween the display processor reference the sensor processor reference.As illustrated in FIG. 5A, the display processor system ground isprovided to each reference input for each receiver channel and referencechannel.

Referring to FIG. 5A, in one embodiment, the processing system 210further comprises a reference channel 380 configuration in which thefirst input port(s) 434, 435 of the reference channel(s) 380 aredirectly coupled to the output of the drive voltage supply 320. In thisconfiguration, the transmitter signal delivered from the drive voltagesupply 320 is delivered to one or more of the transmitter electrodes 260(and one or more common electrodes) and also provided as a referencechannel input signal coupled through the input capacitors C_(R1), C_(R2)(a first and second capacitor reference) of the first input ports 434,435, respectively, through line 503. In one embodiment, the drivevoltage supply may be provided as a reference channel input signalcoupled through an AC coupling that is external to the sensor processor360. The received reference channel input signal is then processed bythe circuitry in each of the reference channels 380 ₁, 380 ₂ to providean reference channel output signal by each of the reference channels 380₁, 380 ₂, which may be used by one or more receiver channels 370(receiver channels 370 ₁-370 _(N)), analysis module 390 and/orelectronic system 250 to substantially reduce interference due todifferences between the display processor reference and the sensorprocessor reference. In one embodiment, the reference channel outputsignal(s) may be used to set the voltage range of one or more elementsof the receiver channel (e.g., an analog-to-digital converter, or thelike). In this way, changes in or interference on the display drivevoltage may tracked by the sensor processor reference channels.

Referring to FIG. 5B, in one embodiment, the processing system 210further comprises a reference channel 380 configuration in which thefirst input port(s) 434, 435 of the reference channel(s) 380 aredirectly coupled to the output of the drive voltage supply 320 and ACcoupled to the display processor reference voltage. In thisconfiguration, the transmitter signal delivered from the drive voltagesupply 320 is delivered to one or more of the transmitter electrodes 260(and one or more common electrodes) and also provided as a referencechannel input signal coupled through the input capacitors C_(R1),C_(R2)(a first and second capacitor reference) of the first input ports 434,435, respectively. Further, the display processor reference signal iscoupled to the first input ports 434 and 435 through capacitors C_(G1)and C_(G2), as illustrated in FIG. 5B. While capacitors C_(G1) andC_(G2) are illustrated as being external to sensor processor 360,however, in other embodiments, one or both capacitors C_(G1) and C_(G2)may be internal to sensor processor 360. Further, while two capacitors,capacitors C_(G1) and C_(G2), are illustrated, in other embodiments,only a single capacitor may be implemented. In one embodiment, the drivevoltage supply may be provided as a reference channel input signalcoupled through an AC coupling that is external to the sensor processor360. The received reference channel input signal is then processed bythe circuitry in each of the reference channels 380 ₁, 380 ₂ to providean reference channel output signal by each of the reference channels 380₁, 380 ₂, which may be used by one or more receiver channels 370(receiver channels 370 ₁-370 _(N)), analysis module 390 and/orelectronic system 250 to substantially reduce interference due todifferences between the display processor reference and the sensorprocessor reference. In one embodiment, the reference channel outputsignal(s) may be used to set the voltage range of one or more elementsof the receiver channel (e.g., an analog-to-digital converter, or thelike). In this way, changes in or interference on the display drivevoltage may tracked by the sensor processor reference channels.

Third Input Device Example

FIGS. 6A and 6B are each a schematic view of a portion of the processingsystem 210 of the input device 200 according to another embodiment ofthe invention described herein. As illustrated in FIGS. 6A and 6B, theprocessing system 210 may comprise a display processor 350 and a sensorprocessor 360 that work together to provide input sensing data to ananalysis module 390 and/or electronic system 250. One will note that thecomponents that are similarly numbered and configured, as shown in FIGS.3-5, will not be re-discussed herein.

In one embodiment, as discussed above and shown in FIG. 6A, a sensorprocessor reference signal can be formed by coupling the second inputports 442 ₁-442 _(N) of the receiver channels 370 to the displayprocessor ground 347 of the display processor 350. In someconfigurations, as illustrated in FIGS. 4-7, a system capacitance C_(GS)couples the second input ports 442 ₁-442 _(N) and the display processorground 347 of the display processor 350. In one embodiment, systemcapacitance C_(GS) may be internal to sensor processor 360. In otherconfigurations, as illustrated in 6B, the display processor referencesignal may be AC coupled (C_(R1) and C_(R2)) to the input of each of thereference channels through line 621, such that each reference channelinput signal is based, at least in part, on the interference within thedisplay processor reference signal. Further, in such configurations, thereference channel output signals comprise effects corresponding to theinterference within the display processor reference signal. The ACcoupling may be internal to, or external to the sensor processor or thedisplay processor. One will note, as is described above, the resultingsignals received with each of the receiver electrodes 270 ₁-270 _(N) andthe first input ports 441 ₁-441 _(N) may include interference created bythe difference between the display processor reference the sensorprocessor reference.

In one embodiment, as illustrated in FIGS. 6A and 6B, the processingsystem 210 may further comprise an external triggering device 613 and alevel shifter 615 that are used to coordinate transmitter signals fromthe display processor 350 with the sensing operation of the sensorprocessor 360. In one embodiment, the external triggering device 613 isused to control the timing of the capacitive sensing operation bydelivering communication signals, such as triggering waveforms ortriggering pulses that are received by the drive voltage supply 320, andtrigger the drive voltage supply 320 to sequentially deliver transmittersignals in a synchronized manner to the transmitter electrodes 260 ₁-260_(N). In some configurations, as shown in FIGS. 6A and 6B, thetriggering pulses that are delivered to the drive voltage supply 320 areprovided from the level shifter 615 that is configured to providetriggering pulses that are at a voltage level and/or voltage range thatdiffers from the voltage level and/or voltage range of the signal (e.g.,a sensor processor transmitter signal or sensor processor triggeringsignal) provided by the external triggering device 613. In someconfigurations, the triggering pulses that are delivered to the drivevoltage supply 320 are provided directly from the external triggeringdevice 613, which is configured to provide a signal that is at a voltagelevel and/or voltage range that differs from the voltage level and/orvoltage range of the capacitance sensing signal provided by the drivevoltage supply 320.

In various embodiments, the level shifter 615 is configured to receivethe triggering pulses from the external triggering device 613, andprovide a voltage level shifted output signal that is used by the chargeaccumulators 432, 433 of the reference channels 380 ₁, 380 ₂ to createreference channel output signals that are used by the receiver channels370 ₁-370 _(N), the analysis module 390 and/or electronic system 250components. In one embodiment, the high output level of the referencechannel input signal, which is delivered to the input ports 434, 435 ofthe charge accumulators 432, 433, is set by the input signal provided tothe level shifter 615 from the output of the power supply. Further, thelow output level of the reference channel input signal, which isreceived at the input ports 434, 435, can be based on the displayprocessor reference signal, which may be coupled to the level shifter615 and the display processor ground 347. In one embodiment, thereceived reference channel input signal is processed by the circuitry ineach of the reference channels 380 ₁, 380 ₂ to provide an referencechannel output signal by each of the reference channels 380 ₁, 380 ₂,which may be used by one or more receiver channels 370 (receiverchannels 370 ₁-370 _(N)), analysis module 390 and/or electronic system250 to substantially reduce interference due to differences between thedisplay processor reference and the sensor processor reference. In oneembodiment, the reference channel output signal(s) may be used to setthe voltage range of one or more elements of the receiver channel (e.g.,an analog-to-digital converter, or the like), reducing the interferencedue to the differences between the display processor and sensorprocessor reference signals.

During a capacitive sensing interval performed by the input device 200,the external triggering device 613 is configured to deliver a series ofpulses that vary between a first voltage level and a second voltagelevel to the level shifter 615. In one example, the first voltage levelis less than about 5 volts and the system ground (e.g., level of point346 (FIG. 3A)). The level shifter 615 then adjusts the level of thereceived signal from the external triggering device 613 based on thehigh and low output level and provides a triggering signal to the drivevoltage supply 320 and a level adjusted signal to the input ports 434,435 of the reference channels 380 ₁, 380 ₂. In one example, the highoutput level 617 supplied by the drive voltage supply 320 may have amagnitude of between 1 and 15 volts. In other embodiments, the lowoutput level supplied on line 619 (which is the display processorreference signal) may have a magnitude of less than 1 volt. In otherembodiments, the high output level supplied on line 617 by the drivevoltage supply 320 may have a magnitude of greater than 15 volts. Thetriggering signal received by the drive voltage supply 320 cause thedrive voltage supply 320 to deliver transmitter signal(s) to thetransmitter electrodes 260 ₁-260 _(N), which is then received andprocessed by the receiver channels 370 ₁-370 _(N) with receiverelectrodes 270 ₁-270 _(N). The reference channel output signal(s),formed by the reference channels 380 ₁, 380 ₂, can then be used byreceiver channels 370 ₁-370 _(N) to provide reliable receiver channeloutput signals to the analysis module 390 and host components.

Fourth Input Device Example

FIGS. 7A and 7B each are a schematic view of a portion of the processingsystem 210 of the input device 200 according to another embodiment ofthe invention described herein. The embodiments illustrated in FIGS. 7Aand 7B are each similar to FIGS. 4A and 4B, except that the referencechannel output signal of the reference channel 380 is provided to theanalysis module 390 and/or the electronic system 250, which thencompares the received reference channel output signal with the ofreceived the receiver channel(s) 370 signal(s) to determine at least aportion of the positional information of the input object. While onereference channel 380 is shown, in other embodiments, multiple referencechannels may be employed. In various embodiments, reference channel 380may further comprise circuitry elements that are adapted to deliver adigital form of the reference channel output signal to the analysismodule 390, such as at least an analog/digital converter (ADC), or thelike.

In one embodiment, the analysis module 390 and/or the electronic system250 is configured to correct the measured capacitance, such as one ofthe capacitances C_(S), based on the resulting signal received from thereceiver channel 370, and use the corrected capacitance value todetermine the positional information of an input object 240 in thesensing region 220 of the input device 200. In this case, the referencechannel output signal delivered from the reference channel 380 is usedto form the corrected capacitance value, which is then used to determinethe presence of an input object 240. During operation, in oneembodiment, a measured capacitance C_(S) at an instant in time t₁, suchas a measured capacitance C_(S1) at time t₁, is multiplied by acorrection factor, which is determined by dividing a reference channeloutput signal taken at the time t₁ by a reference channel output signaltaken at a time t₀ (e.g., a reference channel output signal taken at aprior instant in time or a stored baseline value). In the illustratedembodiment, the magnitude of the reference channel output signalreceived from a reference channel 380 is based on the fixed capacitanceof the input capacitor C_(R) and the voltages of the drive signalprovided by power supply 320. In one embodiment, which comprises morethan one reference channel and reference capacitance, the multiplereference capacitances may be used to correct the sensed capacitance atany instant in time to determine the positional information of an inputobject 240. In one example, the measured capacitance of each referencechannel is corrected by taking the ratio of the reference channel outputsignals at any instants in time.

While a configuration of the processing system 210 that includes thedelivery of the reference channel output signals to the analysis module390 and/or electronic system 250 is described and illustrated herein inconjunction with FIGS. 4A and 4B, this configuration is not intended tobe limiting as to the scope of the invention described herein, since anyof the configurations disclosed herein, such as the ones discussed inconjunction with FIGS. 3-6, could utilize this reference channelconfiguration. For example, the embodiments of FIGS. 7A and 7B maycomprise level shifters as described in relation with FIGS. 6A and 6B.Further, while the embodiments illustrated in FIGS. 7A and 7B areillustrated as having a signal generator 430, in either embodiment,C_(R1) may be coupled with the output of signal generator 420B as isillustrated in FIGS. 5A and 5B.

Further, while the above embodiments may describe transcapacitivesensing embodiments, in various embodiments, input device 200 may beconfigured to sense changes in absolute capacitance. In suchembodiments, sensed capacitance “C_(s)” may be formed between a sensorelectrode and an input object. In such embodiments, a transmitterelectrode, driven by the display processor, is not capacitively coupledto a receiver electrode. To state it another way, in absolutecapacitance sensing embodiments, a sensor electrode is driven andreceived with simultaneously. In one embodiment, with reference to FIGS.3A, 4A, 5A and 6A, reference channel input port 384 may be coupled asensor processor reference signal 346 which may be based on a displayprocessor reference signal (e.g., display processor reference signal347). Further, reference channel input port 383 may be capacitivelycoupled to sensor processor reference signal 346 (or some otherreference signal of input device 200) through a reference capacitance(C_(R)). In such embodiments, line 381 or 472 may comprise a capacitivecoupling to sensor processor reference signal 346 instead of the drivevoltage supply 320. With reference to FIGS. 3B, 4B, 5B and 6B, referencechannel 380 comprises input connection 395 that is capacitively coupledto a display processor reference voltage (e.g., display processorreference signal 347, Vcom, etc.) through connection 343-2, andreference channel input port 383 that is capacitively coupled to sensorprocessor reference signal 346 (or some other reference signal of theinput device 200) through 381. In such an embodiment, line 381 may becapacitive coupled to sensor processor reference signal 346 (or someother reference signal of input device 200) through a referencecapacitance (C_(R)). In the embodiments illustrated in FIGS. 4B, 5B, and6B, the connection 343-2 and input connection 395 (e.g., referencenumeral 474 in FIGS. 4B, 5B, 6B and 7B) are coupled to the first inputport (i.e., input port 383) of reference channel 380, thereby providingthe display reference signal to the first input port. Any interferencethat is present on the display processor reference signal may be coupledinto the reference channel, providing a reference channel output signalthat comprises the interference, which may be used to substantiallyminimize the effects of that interference on the resulting signalsreceived by the receiver channel(s) 370. The embodiments illustrated inFIGS. 7A and 7B may also be configured to operate for absolutecapacitive sensing, as described above. As is described above, in theembodiments illustrated in FIGS. 7A and 7B, the reference channel outputsignal(s) is provided to analysis module 390 along with the receiverchannel output signals. Analysis module 390 is configured to process thereceiver channel output signals and the reference channel output signalsto substantially remove any interference due to the display processorreference signal present in the receiver channel output signal(s).

Further, while in the above description and related figures, the displayprocessor is described as being configured to drive the commonelectrodes for capacitive sensing and display updating, in variousembodiment the above interference mitigation techniques may be appliedto a system where the display processor is configured to drive thecommon electrodes for display updating and a separate processor (e.g.the sensor processor, etc.) may be configured to drive a plurality oftransmitter electrodes for capacitive sensing. In such an embodiment,the transmitter electrodes are separate from the common electrodes.Further, at least part of driver 321 may be present in sensor processor360. In such an embodiment, while the display driver may not beconfigured to drive the transmitter electrodes for capacitive sensing,the above techniques of coupling the display reference signal to thereference channel(s) and/or to the sensor processor reference signal maybe applied (as is described related to FIGS. 3-7).

The embodiments and examples set forth herein were presented in order tobest explain the present technology and its particular application andto thereby enable those skilled in the art to make and use the presenttechnology. Those skilled in the art will recognize that the foregoingdescription and examples have been presented for the purposes ofillustration and example only. The description as set forth is notintended to be exhaustive or to limit the present technology to theprecise form disclosed. While the foregoing is directed to embodimentsof the present invention, other and further embodiments of the inventionmay be devised without departing from the basic scope thereof, and thescope thereof is determined by the claims that follow.

The invention claimed is:
 1. An input device, comprising: a plurality oftransmitter electrodes comprising a plurality of common electrodesconfigured to operate in a first mode for capacitive sensing andconfigured to operate in a second mode for updating a display device; aplurality of receiver electrodes; a display processor coupled to theplurality of transmitter electrodes and configured to drive at least oneof the transmitter electrodes with a transmitter signal for capacitivesensing; and a sensor processor coupled to the plurality of receiverelectrodes and configured to receive resulting signals with theplurality of receiver electrodes when at least one of the commonelectrodes are driven for capacitive sensing, wherein the sensorprocessor comprises one or more receiver channels, and wherein each ofthe one or more receiver channels is coupled to a receiver electrode ofthe plurality of receiver electrodes, and each of the one or morereceiver channels have: a first receiver channel input port configuredto receive at least a portion of the resulting signals; and a secondreceiver channel input port configured to receive a sensor processorreference signal that is based on a display processor reference signal,wherein each of the one or more receiver channels is configured toprovide an output signal based on a comparison of the at least a portionof the resulting signals and the sensor processor reference signal. 2.The input device of claim 1, wherein each of the one or more receiverchannels comprises a charge accumulator, wherein the second receiverchannel input port is coupled to a reference input of the chargeaccumulator.
 3. The input device of claim 1, wherein the displayprocessor reference signal is configured to be electrically coupled to aground of the sensor processor.
 4. The input device of claim 1, whereinthe sensor processor further comprises a reference channel configured toprovide a reference channel output wherein the reference channel has afirst reference channel input port that is configured to receive areference channel input signal and a second reference channel input portthat is in electrical communication with the second receiver channelinput port and is configured to receive the sensor processor referencesignal.
 5. The input device of claim 4, wherein the sensor processorreference signal is based on at least one of the display processorreference signal and a second display processor reference signal.
 6. Theinput device of claim 4, wherein the reference channel input signal isbased on at least one of the display processor reference signal and asecond display processor reference signal.
 7. The input device of claim4, wherein the reference channel input signal is based on thetransmitter signal.
 8. The input device of claim 7, wherein thetransmitter signal is generated from a level shifter that translates asensor processor transmitter signal into voltage levels based on atleast one of the display processor reference signal and a second displayprocessor reference signal.
 9. A sensor processor for an input device,comprising: a sensor circuitry coupled to a plurality of sensorelectrodes, wherein the sensor processor is coupled to a displayprocessor that is configured to drive a plurality of common electrodesfor updating a display device, wherein the sensor processor comprises atleast one receiver channel configured to receive resulting signals withat least one of the plurality of sensor electrodes and to receive asensor processor reference signal that is based on a display processorreference signal, and wherein the receiver channel is further configuredto provide an receiver channel output signal based on at least a portionof the received resulting signals and the sensor processor referencesignal.
 10. The sensor processor of claim 9, wherein the displayprocessor reference signal is configured to be electrically coupled to aground of the sensor processor.
 11. The sensor processor of claim 9,wherein the sensor processor further comprises: a reference channel thatis configured to provide a reference channel output signal, wherein thereference channel is configured to receive a first signal based on thefirst display processor reference signal and wherein an output of thesensor processor is based on the receiver channel output signal and thereference channel output signal.
 12. The sensor processor of claim 11,wherein the reference channel is further configured to receive a secondsignal based on a second display processor reference signal.
 13. Thesensor processor of claim 11, wherein the receiver channel is configuredto provide the receiver channel output signal to an analog-to-digitalconverter and wherein the reference channel is configured to provide thereference channel output signal to the analog-to-digital converter, andwherein the output of the sensor processor that is based on the receiverchannel output signal and the reference channel output signal comprisesthe output of the sensor processor being based on an output of theanalog-to-digital converter.
 14. The sensor processor of claim 9,wherein the display processor is further configured to drive the commonelectrodes for capacitive sensing comprising transmitting a transmittersignal with at least one of the common electrodes, and wherein thesensor processor comprises a reference channel that is configured toreceive at least a portion of the transmitter signal and the sensorprocessor reference signal.
 15. The sensor processor of claim 9, whereinthe sensor processor further comprises a reference channel that has afirst reference channel input port that is configured to receive areference channel input signal and a second reference channel input portthat is in electrical communication with the second receiver channelinput port and is configured to receive the sensor processor referencesignal, wherein the reference channel input signal is based on atransmitter signal that is generated from a level shifter thattranslates a sensor processor transmitter signal into voltage levelsbased on at least one of the display processor reference signal and asecond display processor reference signal.
 16. The sensor processor ofclaim 9, wherein the display processor is further configured to drivethe plurality of common electrodes for capacitive sensing and whereinreceiving resulting signals with the plurality of sensor electrodescomprises receiving resulting signals when the display processor drivesthe plurality of common electrodes for capacitive sensing.
 17. Thesensor processor of claim 9, wherein the sensor processor is furtherconfigured to drive the plurality of sensor electrodes for capacitivesensing, and wherein receiving resulting signals with the plurality ofsensor electrodes comprises receiving the resulting signals with theplurality of sensor electrodes when the sensor processor drives theplurality of sensor electrodes for capacitive sensing.
 18. A processingsystem for an input device, the processing system comprising: a displayprocessor configured to drive a plurality of common electrodes forupdating a display device, the display processor comprising a displayprocessor reference signal, a sensor processor configured to receiveresulting signals from a plurality of sensor electrodes, wherein thesensor processor comprises a first reference channel configured togenerate a first reference channel output signal at least partiallybased on the display processor reference signal, wherein the processingsystem is configured to determine positional information for an inputobject in a sensing region of the input device at least based in part onthe resulting signals and the first reference channel output signal. 19.The processing system of claim 18, wherein the display processor isfurther configured to drive the plurality of common electrodes forcapacitive sensing comprising driving at least one of the plurality ofcommon electrodes with a transmitter signal, wherein receiving resultingsignals from a plurality of sensor electrodes comprises receiving aresulting signal when at least one of the plurality of common electrodesare driven with a transmitter signal, and wherein the first referencechannel output signal is further generated based on the transmittersignal.
 20. A processing system for an input device of claim 19, whereinthe first reference channel is further configured to receive a firstreference channel input signal based on at least part of the transmittersignal and the display processor reference signal.
 21. The displayprocessor of claim 20, wherein receiving the first reference channelinput signal based on at least part of the transmitter signal whereinthe transmitter signal is generated from a level shifter that translatesa sensor processor transmitter signal into voltage levels based on atleast one of the display processor reference signal and a second displayprocessor reference signal.
 22. The processing system of claim 18,wherein the display processor is further configured to drive theplurality of common electrodes for capacitive sensing comprising drivingat least one of the plurality of common electrodes with a transmittersignal, wherein the transmitter signal comprises a waveform thattransitions from a first voltage potential to a second voltagepotential, wherein receiving resulting signals from a plurality ofsensor electrodes comprises receiving a resulting signal when at leastone of the plurality of common electrodes are driven with a transmittersignal, and wherein the first reference channel output signal is furthergenerated based on a modulated signal that is based on the first voltagepotential.
 23. The processing system of claim 18, wherein the firstreference channel is further configured to receive a first referencechannel input signal based on at least part of a transmitter signal anda second reference channel input signal that is based on the displayprocessor reference signal.
 24. The processing system of claim 18,wherein the sensor processor comprises one or more receiver channels,and wherein each of the one or more receiver channels is coupled to asensor electrode of the plurality of sensor electrodes, and each of theone or more receiver channels has: a first receiver channel input portconfigured to receive at least a portion of the resulting signals; and asecond receiver channel input port configured to receive a sensorprocessor reference signal that is based in part on the displayprocessor reference signal, wherein each of the one or more receiverchannels is configured to provide a receiver channel output signal basedon a comparison of the signals received at the first receiver channelinput port and the second receiver channel input port.
 25. Theprocessing system of claim 18, wherein the display processor referencesignal is configured to be electrically coupled to a system ground ofthe sensor processor.
 26. The processing system of claim 18, wherein thefirst reference channel is further configured to receive a firstreference channel input signal that is based on a transmitter signalthat is generated from a level shifter that translates a sensorprocessor transmitter signal into voltage levels based on at least oneof the display processor reference signal and a second display processorreference signal.
 27. The processing system of claim 18, wherein thesensor processor is further configured to drive the plurality of sensorelectrodes for capacitive sensing, and wherein receiving the resultingsignals from the plurality of sensor electrodes comprises receiving theresulting signals from the plurality of sensor electrodes when theplurality of sensor electrodes are driven for capacitive sensing. 28.The processing system of claim 27, wherein driving the plurality ofsensor electrodes for capacitive sensing comprises driving the pluralityof sensor electrodes with a signal comprising a waveform thattransitions from a first voltage potential to a second voltagepotential, and wherein the first reference channel is configured toreceive a generated modulated signal that is based on the first voltagepotential.
 29. A method of sensing an input object in a sensing regionof an input device, comprising: driving a display update on at least oneof a plurality of common electrodes, the common electrodes configuredfor capacitive sensing and updating a display device; driving atransmitter signal onto at least one of a plurality of commonelectrodes; receiving a resulting signal from one or more receiverelectrodes, wherein the resulting signal comprises effects correspondingto the transmitter signal; and comparing the resulting signal with asensor processor reference signal that is based on a display processorreference signal.
 30. The method of claim 29, wherein comparing theresulting signal with the sensor processor reference signal furthercomprises: providing the resulting signal to a first input of a chargeaccumulator; and providing the sensor processor reference signal to asecond input of the charge accumulator, wherein the charge accumulatoris configured to: form a receiver channel output signal using theresulting signal and the sensor processor reference signal; and outputthe receiver channel output signal to a host system for sensing thepresence of an object near the one or more receiver electrodes.
 31. Themethod of claim 29, wherein comparing the resulting signal with thesensor processor reference signal further comprises: providing theresulting signal to a receiver channel; providing the display processorreference signal to a reference channel; and comparing the output of thereceiver channel to the output of the reference channel.
 32. The methodof claim 31, further comprising: outputting the receiver channel outputsignal to a host system to provide data for sensing the input object inthe sensing region of the input device.
 33. The method of claim 29,wherein driving the transmitter signal is provided by a displayprocessor, and driving of the transmitter signal is based on acommunication signal provided by a sensor processor, said sensorprocessor coupled to the one or more receiver electrodes, wherein themethod further comprises: level shifting the communication signal,wherein level shifting comprises: receiving the communication signal;and adjusting the voltage level of the received communication signal toform an adjusted communication signal; and delivering the adjustedcommunication signal to the display processor or a reference channeldisposed in the sensor processor.